Securing a Stormont deal would have been fitting memorial to their late colleague, says Alban Maginness.

By abruptly ending the negotiations in Stormont on Sunday, Sinn Fein are dishonouring the political legacy of Martin McGuinness. To truly honour his memory, Sinn Fein should be still up there in the Assembly, hammering out a deal with the DUP to restore a new power-sharing Executive. If his political journey meant anything, it meant that a power-sharing Executive could successfully transform politics here from conflict to harmony.

It may be no coincidence that, when his health was at its lowest ebb, he resigned as Deputy First Minister. Whether he did so willingly, or not, remains to be seen.

There is a credible suspicion that a seriously weakened Martin McGuinness gave in to the demands of the more hawkish grassroots elements within the republican movement to let the institutions fall and severely punish the DUP.

Gerry Adams's graveside oration, with its unnecessarily provocative reference to McGuinness as a freedom fighter, not a terrorist, emphasises an increasingly hardline position.

The re-emergence of Adams in the Stormont negotiations, and his personal appointment of Michelle O'Neill, indicates that he is still the supreme leader. O'Neill is viewed as a puppet.

Publicly, she is never seen without being in his presence and has adopted a clearly deferential political role, something that McGuinness would never have tolerated. Sinn Fein's withdrawal from the talks means their preference now is for another election, to finish off the DUP's slim majority.

Throughout his remarkable journey, from physical force republican to becoming a constitutional nationalist, he used his considerable personal authority to persuade the IRA that the long war of attrition with the British could not achieve victory.

His outreach to unionists was genuine. It is no accident that the most impressive tributes on his death have come from the Paisley family, Peter Robinson and Lord Trimble.

Arlene Foster gave a generous tribute to him in the Assembly and her attendance at the funeral Mass was an act of conciliation that was publicly applauded.

Unlike the more sinister persona of Gerry Adams, McGuinness, by dint of his engaging personality, developed a level of trust that produced a good working relationship with Ian Paisley and Peter Robinson. Unfortunately, that relationship did not spread throughout the body politic.

Nonetheless, it was a considerable achievement and sustained the Assembly and the Executive, albeit imperfectly, for a decade.

Listening back to TV interviews from the time he was a young IRA man, McGuinness sounded raw and immature, when he admitted that, as a teenager, he joined the IRA because the Catholic community were being treated as third-class citizens.

Despite his undoubted journey to peace, what is most disappointing about McGuinness is not simply his failure to disown the use of violence by the Provos, but his attempt to still justify their use of violence.

He said that the circumstances in Derry in the 1970s were such that he, as well as others, had no other choice but to join the IRA.

This is insulting to thousands of ordinary young people in Derry who did not feel forced by circumstances to join the IRA.

It also ignores the fact that there was another alternative available; that is the path of peaceful constitutional nationalism forged by fellow Derryman and SDLP leader, John Hume.

Hume taught that justice, equality and, indeed, reunification could be achieved through gradual political change. It was Hume's bold vision of peaceful change that McGuinness ultimately adopted.

In addition, his failure to reject IRA violence is dangerously supportive of the dissident republican argument that armed struggle is still a legitimate political act.

After all, the Provo campaign was devoid of any democratic mandate. Surely, in his heart, he must have realised that the campaign itself was counterproductive to the declared aim of a united Ireland?

The fact is that the IRA campaign put back a united Ireland by many years, because it further divided the people of Northern Ireland and of Ireland as a whole.

So much, then, for his boastful assertion, as an angry young man, that a united Ireland would only be brought about by the "cutting edge of the IRA".

Regrettably, there have been some hateful comments about his death. Lord Tebbit's unrepeatable remarks were grossly offensive and pathetic. But we must understand people's deep feelings about the injustice created by the IRA campaign.

Many other people have been grappling with their mixed feelings about Martin McGuinness, and sympathy must be given to those who find it too hard to forgive.

You cannot force people to forgive, but, sadly, if they don't forgive, it will be their own loss, for their humanity will be diminished and their hurt unhealed.

C S Lewis, the great Christian writer, said: "To be Christian means to forgive the inexcusable, because God has forgiven the inexcusable in you."